The present invention broadly relates to light reflectors having thin film coatings applied thereto for selective reflectance and transmission of different portions of the electromagnetic spectrum radiating from a source. The present invention more particularly relates to such reflectors having plural coatings with different reflectance/transmittance properties across the electromagnetic spectrum, the different coatings being applied to different, pre-selected portions of the reflector, respectively.
Light reflectors come in a variety of types and configurations. A common reflector configuration comprises a generally dome-shaped reflecting portion with a rearwardly extending neck portion wherein a lamp (typically of the incandescent or halogen type) is secured for radiating light forwardly of the reflector body. The reflector body may be made totally reflecting, wherein substantially all of the electromagnetic spectrum emitted by the lamp is reflected forwardly, or it can be of the "cold-mirror" type wherein an optical interference coating is applied to a transparent reflector body (typically glass) with the interference coating acting as a light filter to reflect most of the visible light of the spectrum while transmitting most of the infra-red component thereof (hereinafter "IR") through the transparent reflector body. Since the IR component is the source of heat in the electromagnetic spectrum, the visible light reflected forward is considered "cold" light which is desirable in many reflector applications.
Certain drawbacks have been identified with cold mirror reflectors, the most prominent of which is the uncontrolled transmission of IR radiation through the reflector body which may cause damage by over-heating of components positioned rearwardly of the reflector body (e.g., transformers and plugs). Another feature of the cold mirror reflector which many find objectionable is the escape of visible light through the end portion of the neck, the internal cavity of which is a difficult area to coat with typical techniques used for applying thin films to reflector bodies (e.g., evaporation and sputtering in a vacuum). The visual attractiveness of the reflector itself and the illumination pattern it creates in the surrounding area are also concerns, as well as being able to coat the reflectors in an efficient, in-line process.